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Commit c3fb76db authored by Igor Babaev's avatar Igor Babaev
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BNL and BNLH algorithms scan the join table and for each its record they 

try to find a match in the join buffer. It makes sense to check for a match
only those records satisfying WHERE/ON conditions that can be pushed to
the scanned table. It allows us to discard early some join candidates.

Such pushdown conditions were built when BNL join algorithm was employed,
but for they were not built when BNLH algorithm was used.
The patch removes this shortcoming.
parent 3d8c7a2c
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Showing with 78 additions and 37 deletions
sql/sql_select.cc
View file @ c3fb76db
......@@ -179,12 +179,14 @@ static int join_ft_read_next(READ_RECORD *info);
int join_read_always_key_or_null(JOIN_TAB *tab);
int join_read_next_same_or_null(READ_RECORD *info);
static COND *make_cond_for_table(Item *cond,table_map table,
table_map used_table,
bool exclude_expensive_cond);
table_map used_table,
bool exclude_expensive_cond,
bool retain_ref_cond);
static COND *make_cond_for_table_from_pred(Item *root_cond, Item *cond,
table_map tables,
table_map used_table,
bool exclude_expensive_cond);
bool exclude_expensive_cond,
bool retain_ref_cond);
static Item* part_of_refkey(TABLE *form,Field *field);
uint find_shortest_key(TABLE *table, const key_map *usable_keys);
......@@ -927,7 +929,7 @@ JOIN::optimize()
if (conds && !(thd->lex->describe & DESCRIBE_EXTENDED))
{
COND *table_independent_conds=
make_cond_for_table(conds, PSEUDO_TABLE_BITS, 0, FALSE);
make_cond_for_table(conds, PSEUDO_TABLE_BITS, 0, FALSE, FALSE);
DBUG_EXECUTE("where",
print_where(table_independent_conds,
"where after opt_sum_query()",
......@@ -2254,7 +2256,7 @@ JOIN::exec()
Item* sort_table_cond= make_cond_for_table(curr_join->tmp_having,
used_tables,
(table_map)0, FALSE);
(table_map)0, FALSE, FALSE);
if (sort_table_cond)
{
if (!curr_table->select)
......@@ -2277,7 +2279,7 @@ JOIN::exec()
QT_ORDINARY););
curr_join->tmp_having= make_cond_for_table(curr_join->tmp_having,
~ (table_map) 0,
~used_tables, FALSE);
~used_tables, FALSE, FALSE);
DBUG_EXECUTE("where",print_where(curr_join->tmp_having,
"having after sort",
QT_ORDINARY););
......@@ -5979,6 +5981,46 @@ bool JOIN_TAB::hash_join_is_possible()
}
/*
@brief
Extract pushdown conditions for a table scan
@details
This functions extracts pushdown conditions usable when this table is scanned.
The conditions are extracted either from WHERE or from ON expressions.
The conditions are attached to the field cache_select of this table.
@note
Currently the extracted conditions are used only by BNL and BNLH join.
algorithms.
@retval 0 on success
1 otherwise
*/
int JOIN_TAB::make_scan_filter()
{
COND *tmp;
DBUG_ENTER("make_join_select");
Item *cond= is_last_inner_table() ?
*get_first_inner_table()->on_expr_ref : join->conds;
if (cond &&
(tmp=make_cond_for_table(cond, join->const_table_map | table->map,
table->map, FALSE, TRUE)))
{
DBUG_EXECUTE("where",print_where(tmp,"cache", QT_ORDINARY););
if (!(cache_select=
(SQL_SELECT*) join->thd->memdup((uchar*) select, sizeof(SQL_SELECT))))
DBUG_RETURN(1);
cache_select->cond= tmp;
cache_select->read_tables=join->const_table_map;
}
DBUG_RETURN(0);
}
static uint
cache_record_length(JOIN *join,uint idx)
{
......@@ -6751,7 +6793,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
COND *const_cond=
make_cond_for_table(cond,
join->const_table_map,
(table_map) 0, TRUE);
(table_map) 0, TRUE, FALSE);
/* Add conditions added by add_not_null_conds(). */
for (uint i= 0 ; i < join->const_tables ; i++)
add_cond_and_fix(&const_cond, join->join_tab[i].select_cond);
......@@ -6765,7 +6807,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
JOIN_TAB *cond_tab= tab->first_inner;
COND *tmp= make_cond_for_table(*tab->on_expr_ref,
join->const_table_map,
( table_map) 0, FALSE);
(table_map) 0, FALSE, FALSE);
if (!tmp)
continue;
tmp= new Item_func_trig_cond(tmp, &cond_tab->not_null_compl);
......@@ -6853,7 +6895,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
tmp= NULL;
if (cond)
tmp= make_cond_for_table(cond, used_tables, current_map, FALSE);
tmp= make_cond_for_table(cond, used_tables, current_map, FALSE, FALSE);
/* Add conditions added by add_not_null_conds(). */
if (tab->select_cond)
add_cond_and_fix(&tmp, tab->select_cond);
......@@ -6912,7 +6954,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
if (thd->variables.engine_condition_pushdown && !first_inner_tab)
{
COND *push_cond=
make_cond_for_table(tmp, current_map, current_map, FALSE);
make_cond_for_table(tmp, current_map, current_map, FALSE, FALSE);
if (push_cond)
{
/* Push condition to handler */
......@@ -7037,19 +7079,9 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
if (i != join->const_tables && tab->use_quick != 2 &&
!tab->first_inner)
{ /* Read with cache */
if (cond &&
(tmp=make_cond_for_table(cond,
join->const_table_map |
current_map,
current_map, FALSE)))
{
DBUG_EXECUTE("where",print_where(tmp,"cache", QT_ORDINARY););
tab->cache_select=(SQL_SELECT*)
thd->memdup((uchar*) sel, sizeof(SQL_SELECT));
tab->cache_select->cond=tmp;
tab->cache_select->read_tables=join->const_table_map;
}
}
if (tab->make_scan_filter())
DBUG_RETURN(1);
}
}
}
......@@ -7071,7 +7103,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
JOIN_TAB *cond_tab= join_tab->first_inner;
COND *tmp= make_cond_for_table(*join_tab->on_expr_ref,
join->const_table_map,
(table_map) 0, FALSE);
(table_map) 0, FALSE, FALSE);
if (!tmp)
continue;
tmp= new Item_func_trig_cond(tmp, &cond_tab->not_null_compl);
......@@ -7106,7 +7138,7 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
current_map= tab->table->map;
used_tables2|= current_map;
COND *tmp_cond= make_cond_for_table(on_expr, used_tables2,
current_map, FALSE);
current_map, FALSE, FALSE);
add_cond_and_fix(&tmp_cond, tab->on_precond);
if (tmp_cond)
{
......@@ -7686,7 +7718,8 @@ uint check_join_cache_usage(JOIN_TAB *tab,
if ((cache_level <=4 && !no_hashed_cache) || no_bka_cache ||
((flags & HA_MRR_NO_ASSOCIATION) && cache_level <=6))
{
if (!tab->hash_join_is_possible())
if (!tab->hash_join_is_possible() ||
tab->make_scan_filter())
goto no_join_cache;
if (cache_level == 3)
prev_cache= 0;
......@@ -14874,6 +14907,7 @@ bool test_if_ref(Item *root_cond, Item_field *left_item,Item *right_item)
used_table Table that we're extracting the condition for (may
also include PSEUDO_TABLE_BITS
exclude_expensive_cond Do not push expensive conditions
retain_ref_cond Retain ref conditions
DESCRIPTION
Extract the condition that can be checked after reading the table
......@@ -14899,16 +14933,18 @@ bool test_if_ref(Item *root_cond, Item_field *left_item,Item *right_item)
static Item *
make_cond_for_table(Item *cond, table_map tables, table_map used_table,
bool exclude_expensive_cond)
bool exclude_expensive_cond, bool retain_ref_cond)
{
return make_cond_for_table_from_pred(cond, cond, tables, used_table,
exclude_expensive_cond);
exclude_expensive_cond,
retain_ref_cond);
}
static Item *
make_cond_for_table_from_pred(Item *root_cond, Item *cond,
table_map tables, table_map used_table,
bool exclude_expensive_cond)
bool exclude_expensive_cond,
bool retain_ref_cond)
{
if (used_table && !(cond->used_tables() & used_table) &&
......@@ -14939,7 +14975,8 @@ make_cond_for_table_from_pred(Item *root_cond, Item *cond,
{
Item *fix=make_cond_for_table_from_pred(root_cond, item,
tables, used_table,
exclude_expensive_cond);
exclude_expensive_cond,
retain_ref_cond);
if (fix)
new_cond->argument_list()->push_back(fix);
}
......@@ -14971,7 +15008,8 @@ make_cond_for_table_from_pred(Item *root_cond, Item *cond,
{
Item *fix=make_cond_for_table_from_pred(root_cond, item,
tables, 0L,
exclude_expensive_cond);
exclude_expensive_cond,
retain_ref_cond);
if (!fix)
return (COND*) 0; // Always true
new_cond->argument_list()->push_back(fix);
......@@ -14992,7 +15030,8 @@ make_cond_for_table_from_pred(Item *root_cond, Item *cond,
table_count times, we mark each item that we have examined with the result
of the test
*/
if (cond->marker == 3 || (cond->used_tables() & ~tables) ||
if ((cond->marker == 3 && !retain_ref_cond) ||
(cond->used_tables() & ~tables) ||
/*
When extracting constant conditions, treat expensive conditions as
non-constant, so that they are not evaluated at optimization time.
......@@ -15007,13 +15046,13 @@ make_cond_for_table_from_pred(Item *root_cond, Item *cond,
{
Item *left_item= ((Item_func*) cond)->arguments()[0]->real_item();
Item *right_item= ((Item_func*) cond)->arguments()[1]->real_item();
if (left_item->type() == Item::FIELD_ITEM &&
if (left_item->type() == Item::FIELD_ITEM && !retain_ref_cond &&
test_if_ref(root_cond, (Item_field*) left_item,right_item))
{
cond->marker=3; // Checked when read
return (COND*) 0;
}
if (right_item->type() == Item::FIELD_ITEM &&
if (right_item->type() == Item::FIELD_ITEM && !retain_ref_cond &&
test_if_ref(root_cond, (Item_field*) right_item,left_item))
{
cond->marker=3; // Checked when read
......@@ -16198,7 +16237,7 @@ static bool fix_having(JOIN *join, Item **having)
DBUG_EXECUTE("where",print_where(*having,"having", QT_ORDINARY););
Item* sort_table_cond=make_cond_for_table(*having, used_tables, used_tables,
FALSE);
FALSE, FALSE);
if (sort_table_cond)
{
if (!table->select)
......@@ -16216,7 +16255,8 @@ static bool fix_having(JOIN *join, Item **having)
DBUG_EXECUTE("where",print_where(table->select_cond,
"select and having",
QT_ORDINARY););
*having= make_cond_for_table(*having,~ (table_map) 0,~used_tables, FALSE);
*having= make_cond_for_table(*having,~ (table_map) 0,~used_tables,
FALSE, FALSE);
DBUG_EXECUTE("where",
print_where(*having,"having after make_cond", QT_ORDINARY););
}
......
sql/sql_select.h
View file @ c3fb76db
......@@ -394,6 +394,7 @@ typedef struct st_join_table {
}
double get_partial_join_cardinality() { return partial_join_cardinality; }
bool hash_join_is_possible();
int make_scan_filter();
} JOIN_TAB;
......@@ -1038,7 +1039,7 @@ class JOIN_CACHE :public Sql_alloc
}
JOIN_TAB *get_next_table(JOIN_TAB *tab);
friend class JOIN_CACHE_HASHED;
friend class JOIN_CACHE_BNL;
friend class JOIN_CACHE_BKA;
......
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